It is well known that hydrocarbon distillates can be reformed in the presence of catalysts containing one or more Group VIII noble metals. Until recently, the preferred Group VIII noble metal has been platinum. Typical platinum reforming catalysts comprise platinum, a halogen, a promoter such as rhenium, and a refractory inorganic support material, such as a catalytically active alumina.
Webb, in U.S. Pat. No. 2,848,377, discloses the use of a catalyst containing platinum (about 0.01 to 1 wt.%) and iridium (about 0.01 to 1 wt.%) on alumina for the conversion of hydrocarbons, e.g., the reforming of petroleum naphthas. The catalyst can also contain about 0.1 to 10 wt.% of a cracking adjuvant, such as silica or a halogen.
Kearby, in U.S. Pat. No. 2,708,187, teaches the addition of a stabilizing oxide in the form of a protective colloid, such as the hydrated oxides of chrominum, zirconium, thorium, titanium, or iron, to a catalyst containing a Group VIII noble metal, such as platinum, palladium, rhodium, and iridium, on a catalyst support, such as alumina. This addition can markedly reduce the crystal growth tendency of amorphous or colloidal Group VIII noble metal deposited on the surface of the catalyst support and the resulting catalyst can withstand repeated oxidative regenerations without marked activity loss.
Bertolacini, et al., in U.S. Pat. No. 3,943,050, disclose the use of a catalyst comprising a Group VIII noble metal and a small amount of zirconium (about 0.05 wt.% to about 5 wt.% zirconium calculated as the element) on a porous refractory inorganic oxide, such as alumina, as the second catalyst in a two-catalyst process for the reforming of hydrocarbon streams.
Buss, in U.S. Pat. No. 3,554,902; Sinfelt, et al., in U.S. Pat. No. 3,850,747; Sinfelt, et al., in U.S. Pat. No. 3,835,034; Paynter, et al., U.S. Pat. No. 3,950,270; Sinfelt, in U.S. Pat. No. 3,956,190; and Sinfelt, et al., in U.S. Pat. No. 4,018,670, disclose reforming with catalysts comprising platinum and/or iridium on a support comprising one or more refractory inorganic oxides, such as alumina, silica, and zirconia.
Now it has been found that a catalyst comprising iridium, zirconia, and alumina and having the zirconia present in specific amounts provides an improved catalyst for the reforming of naphthas and hydrocarbon streams boiling in the gasoline boiling range.